Diesel and direct injection gasoline engines have fuel injection systems that directly inject fuel into engine cylinders. The fuel is injected to an engine cylinder at a higher pressure so that fuel can enter the cylinder during the compression stroke when cylinder pressure is higher. The fuel is elevated to the higher pressure by a mechanically driven fuel pump. Fuel pressure at the outlet of the fuel pump is controlled by adjusting an amount of fuel that flows through the fuel pump. One way to control flow through the fuel pump is via a solenoid operated metering valve. In one example, the solenoid is operated to close the metering valve during a pumping phase of the fuel pump. Closing the metering valve prevents fuel from flowing into or out of an inlet of the fuel pump. The closing time of the metering valve may be adjusted to control flow through the fuel pump. However, when the solenoid changes state to allow the metering valve to open or close, the solenoid or a portion of metering valve impacts a surface within the metering valve housing. The impact can produce a ticking sound that may not be desirable.
The inventors herein have recognized the above-mentioned disadvantages and have developed a fuel system, comprising: a cam driven fuel pump including an inlet and an outlet; a fuel injector in fluidic communication with the outlet; and a cam driven metering valve positioned at the inlet of the cam driven fuel pump.
By operating the metering valve via a cam, it may be possible to reduce the impact velocity between a metering valve and housing. As a result, a cam that operates the metering valve can be rotated with very little noise. Additionally, the cam operated metering valve can open without producing a striking noise. Consequently, both metering valve opening and closing noises may be reduced as compared to a solenoid operated metering valve.
The present description may provide several advantages. Specifically, the approach may reduce fuel system noise. Further, the approach may provide for improved fuel pressure control. Further still, the approach may improve metering valve durability by reducing impact forces between metering valve components.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.